Engineering data management systems and computer aided design systems provide useful environments for designers of mechanical components to specify the physical characteristics and configurations of various features. Sophisticated computer aided design systems have also been able to provide designers with the ability to specify other information related to the construction and testing of these components. For example, some sophisticated computer aided design systems allow for the designer to specify the type of material to be used to construct a particular component, the tolerances associated with various dimensions of the feature, processing techniques to be used to manufacture the component and other characteristics associated with the manufacture, testing, or use of components of the assembly.
Currently, CAD systems allow the user to restrict the feature's degree of freedom by using a datum in a tolerance. Datums are generally compiled in datum reference frames. Present systems allow any datums to be selected to populate a datum reference frame.